Plymouth’s boxy Belvedere GTX may have been late to the mid-size muscle car market in 1967, but the division stole a march on everybody else in 1968 with the Road Runner.

This time Plymouth got it right; putting a 335 bhp 383 cid V-8 engine with 440 Super Commando heads and camshaft in a bare bones 3,000-lb, two-door hardtop with a 4-speed floor-shift synchro transmission. Base price was $2,870, skinned down to a rubber floor mat and non-pleat taxicab interior. A total of 29,240 buyers bought the coupe and a further 15,359 stepped up for the two-door hardtop – which was added mid-year – for the 44,559 total.

If you wanted carpet and brightwork you had to spend $79.20 for the décor group. The 425 bhp, 426 cid Street Hemi cost another $714.30. But the base car was quick and simple, and capped by a charming beep-beep Road Runner cartoon horn, which supposedly cost $50,000 to license from Warner Brothers (plus $10,000 to develop the beep-beep sound).

Road testers enjoyed the performance, but were less charitable about the drum brakes and the lack of traction off the line. While 0-60 came up in 7.3 seconds, the quarter mile took 15.37 at 91.4 mph and top speed was 122 mph.

The Road Runner was a bargain-basement performance version of the Belvedere and Satellite lineups. To confuse the picture, there was a Satellite two-door hardtop (at 46,539, the top seller) and a Sport Satellite hardtop with 21,014 buyers. These could be ordered with numerous options but they weren’t as focused.

If you wanted a performance hardtop with more luxury and a base 375 bhp, 440 cid Super Commando engine, the GTX was the performance version of the Sport Satellite and closely resembled the Road Runner. Base price was $3,329, with a convertible available from $3,590. A total of 17,914 hardtops, but only 1,026 convertibles were sold. The 425 bhp, 426 Street Hemi was optional, though it was only fitted to 410 hardtops and about 36 convertibles.

At the end of the year, Plymouth sales had risen 12 percent and the division remained the number four U.S. automaker in the sales race.

Popular Road Runner and GTX options included an automatic transmission ($299), air conditioning ($355), Road Runner stripes ($15), blackout hood ($18 for Road Runner and GTX), AM/FM stereo tape ($195), vinyl roof ($79), heavy duty Sure-Grip differential ($146), Super Commando 375 bhp 440 V-8 ($281 for Road Runner), and 425 bhp, 426 cid Street Hemi ($605 for GTX).

Plymouth offered 21 mostly metallic colors, and six interior shades. The colors and codes were Buffed Silver (A), Black (B), Mist Blue (D), Midnight Blue (E), Mist Green (F), Forest Green (G), Yellow Gold (H), Ember Gold (J), Mist Turquoise (K), Surf Turqoise (L), Turbine Bronze (M), Matador Red (P), Electric Blue (Q), Burgundy (R), Sunflower Yellow (S), Avocado Green (T), Frost Blue (U), Sable White (W), Satin Beige (X), Sierra Tan (Y), and Hawaian Blue (2). Interior colors included Majesty Gold, Pampas Tan, Catawba Green, Bahama Blue, Aztec Maroon, and Jewel Black.